From 37407ea7f93864c2cfc03edf8f37872ec539ea2b Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 16 Sep 2012 12:29:43 -0700 Subject: Revert "sched: Improve scalability via 'CPU buddies', which withstand random perturbations" This reverts commit 970e178985cadbca660feb02f4d2ee3a09f7fdda. Nikolay Ulyanitsky reported thatthe 3.6-rc5 kernel has a 15-20% performance drop on PostgreSQL 9.2 on his machine (running "pgbench"). Borislav Petkov was able to reproduce this, and bisected it to this commit 970e178985ca ("sched: Improve scalability via 'CPU buddies' ...") apparently because the new single-idle-buddy model simply doesn't find idle CPU's to reschedule on aggressively enough. Mike Galbraith suspects that it is likely due to the user-mode spinlocks in PostgreSQL not reacting well to preemption, but we don't really know the details - I'll just revert the commit for now. There are hopefully other approaches to improve scheduler scalability without it causing these kinds of downsides. Reported-by: Nikolay Ulyanitsky Bisected-by: Borislav Petkov Acked-by: Mike Galbraith Cc: Andrew Morton Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index b8c86648a2f9..23bddac4bad8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -954,7 +954,6 @@ struct sched_domain { unsigned int smt_gain; int flags; /* See SD_* */ int level; - int idle_buddy; /* cpu assigned to select_idle_sibling() */ /* Runtime fields. */ unsigned long last_balance; /* init to jiffies. units in jiffies */ -- cgit v1.2.3